1. Field of the Invention
This invention relates to a laminated coil which is applicable as a transformer or a coil in a switching power supply such as a DC-DC converter, and also relates to a method for producing such a laminated coil.
2. Description of the Related Art
Heretofore, a laminated coil has been widely produced by using insulating films through development in printed wiring techniques and thin film techniques. Such a laminated coil is usually produced as described below. Firstly, a number of spiral patterns are formed on insulating films. The insulating films are then superimposed one over another. The end portion of the spiral pattern of an insulating film is connected to the beginning portion of the spiral pattern on an upper insulating film by means of the through-hole technique.
In detail, there are provided a plurality of strip-shaped insulating films which have spiral patterns disposed at regular intervals. A first insulating film is let out such as by a sprocket wheel, and a second insulating film is fed over the first insulating film. The end of the spiral pattern of the first insulating film is connected, by the soldering for example, to the beginning of the spiral pattern of the second insulating film via a through-hole. Then, a third insulating film is superimposed on the second insulating film. The end of the spiral pattern of the second film is connected, by soldering for example, to the beginning of the spiral pattern of the third insulating film. Succeeding insulating films are superimposed as described above. The spiral patterns of the first to the n-th insulating films are interconnected so as to obtain laminated coils having a plurality of turns. The insulating films are then cut to separate the coil patterns from one another.
However, with the conventional laminated coil, it has taken time to connect, by soldering for example, the spiral patterns of a pair of adjacent insulating films via the through-hole. In addition, the production line has to be interrupted for the connection of the spiral patterns, thereby reducing the production efficiency of the laminated coils.